Field of the Invention
The present invention relates to a semiconductor relay device of a direct current insulation type having two metal-oxide semiconductor field-effect transistors (MOSFETs) that are connected in series with each other.
Description of Related Art
In this type of insulation type semiconductor relay device, a metal oxide semiconductor (MOS) relay has been known which undergoes an ON-OFF operation by conducting a gate of a MOSFET upon impingement of rays of light, emitted from a light emitting diode (LED), upon a photo diode array. In this respect, see, for example, the patent document 1 listed below. The photo MOS relay referred to above is of a structure in which a signal input circuit and a relay circuit are optically connected with each other, but input and output thereof are electrically insulated.
It has also been known in the art that with the use of two metal-oxide semiconductor field-effect transistors (MOSETs) a signal input circuit and a relay circuit are insulated and separated from each other or are separated on a direct current basis by means of a capacitor. In this respect, see, for example, the patent document 2 listed below. The semiconductor relay device is generally used with a construction including a switching equipment, built therein, and a control panel (CP) which is a relay output side equipment for receiving a relay output and concurrently supplies an electric power to the switching equipment, but if from the standpoint of the control panel (CP), at least a direct current (DC) insulation is possible, the circuit dependency with the switching equipment is dissolved and protection is made from an electric influence thereof.
The semiconductor relay device referred to above is built in a switching equipment of a type, which is required to be silent at the time of a relay operation, for example, in an object detecting sensor for detecting an object and is operable to cause the MOSFET to perform an ON-OFF operation on the basis of an alternating current signal for relay drive purpose that is based on an object detection under the control of a microcomputer (MC) to thereby allow a detection ON-OFF signal to the control panel (CP).